A number of researches are being conducted to provide various types of multimedia services including voice services and to support the high quality and high speed of data transmission in a wireless communication environment. Technologies associated with a multiple-input multiple-output (MIMO) system using multiple channels, are also in rapid development.
An adaptive modulation scheme is widely used in a MIMO system. According to the adaptive modulation scheme, a modulation scheme may be changed as required according to a radio wave state in a wireless channel, for example, reception power, fading, interference, and the like, to thereby achieve a maximum possible data rate. Where a base station modulates a signal according to the adaptive modulation scheme to transmit the modulated signal to a terminal, the terminal may receive and demodulate the modulated signal. Generally, a signal transmitted from the base station may be different from a signal finally received by the terminal due to various interference elements such as noise and the like occurring during a transmission process. Specifically, the signal finally received by the terminal may be varied from the original signal. Accordingly, the terminal may predict a transmission symbol to be transmitted from the base station based on a received symbol, and may reduce a symbol error rate (SER) through a scheme of determining an accurately received symbol to be received where the transmission symbol is errorlessly transmitted.
In order to estimate the transmission symbol based on the received symbol, it may be desirable to determine a modulation order of the signal transmitted from the base station. In particular, the modulation order may vary depending on circumstances in a system using the adaptive modulation scheme and may be an important factor to predict the transmission symbol. Accordingly, there is a need for a method of determining a modulation order.